All materials which meet the criteria of one of the nine (9) hazard classes are regulated as hazardous materials for transport. However, when the amount of certain hazardous material packed within a package is limited, the magnitude of the hazard is reduced but not eliminated. Thus, exceptions can be applied for packaging and hazard communication as authorized for certain hazard classes.
In order to qualify for these exceptions, the US Hazardous Materials Regulations (49 CFR Parts 171?180; HMR), the International Maritime Dangerous Goods Code (IMDG Code), the International Civil Aviation Organization Technical Instructions on the Safe Transport of Dangerous Goods by Air (ICAO TI), Transport Canada’s Transport of Dangerous Goods (TDG), and other international regulatory texts authorize specific quantity limitations per inner and outer packaging for each hazard class and packing group. If the quantity of material contained within the inner packaging is below these limitations, and the gross weight of the outer package is within the authorized limits the consignment may be offered for transportation as a limited quantity.
The HMR, IMDG Code, and TDG typically limit the amount of material allowed within the largest inner packaging in a combination package and limit the gross weight of the package, while the ICAO TI limits the net quantity of hazardous material in the package.
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